1. Field of the Invention
The present invention relates generally to apparatus and methods for removing occluding materials from body lumens. More particularly, the present invention relates to the construction and use of atherectomy catheters for excising atheroma and other materials from blood vessels.
Cardiovascular disease frequently arises from the accumulation of atheromatous material on the inner walls of vascular lumens, particularly arterial lumens of the coronary and other vasculature, resulting in a condition known as atherosclerosis. Atherosclerosis occurs naturally as a result of aging, but may also be aggravated by factors such as diet, hypertension, heredity, vascular injury, and the like. Atheromatous and other vascular deposits restrict blood flow and can cause ischemia which, in acute cases, can result in myocardial infarction. Atheromatous deposits can have widely varying properties, with some deposits being relatively soft and others being fibrous and/or calcified. In the latter case, the deposits are frequently referred to as plaque.
Atherosclerosis can be treated in a variety of ways, including drugs, bypass surgery, and a variety of catheter-based approaches which rely on intravascular widening or removal of the atheromatous or other material occluding a blood vessel. Of particular interest to the present invention, a variety of methods for cutting or dislodging material and removing such material from the blood vessel have been proposed, generally being referred to as atherectomy procedures. Atherectomy catheters intended to excise material from the blood vessel lumen generally employ a rotatable and/or axially translatable cutting blade which can be advanced into or past the occlusive material in order to cut and separate such material from the blood vessel lumen. In particular, side-cutting atherectomy catheters generally employ a housing having an aperture on one side, a blade which is rotated or translated by the aperture, and a balloon or other deflecting structure to urge the aperture against the material to be removed.
Although atherectomy catheters have proven to be very successful in treating many types of atherosclerosis, some catheter designs suffer from certain limitations. For example, many side-cutting atherectomy catheters have difficulty in capturing occluding material in the cutting aperture. To facilitate material capture, the cutting aperture is frequently elongated to increase the area into which the material can penetrate. While such elongation is effective, it requires an equivalent lengthening of the cutter housing. Most cutter housings are rigid, and such lengthening makes it more difficult to introduce the distal end of the catheter through torturous regions of the vasculature. Moreover, having a cutting blade travel over a lengthy cutter aperture increases the risk of penetrating the vascular wall.
For these reasons, it is desired to provide atherectomy catheters which can access even small, tortuous regions of the vasculature and which can remove atheromatous and other occluding materials from within blood vessels in a controlled fashion with minimum risk of injuring the blood vessel wall. In particular, it is desired to provide atherectomy catheters which can facilitate capturing and invaginating atheromatous materials with relatively short cutter mechanisms. The catheters and methods for use in a variety of body lumens, including but not limited to coronary and other arteries. At least some of these objectives will be met by the catheter and method of the present invention described hereinafter and in the claims.
2. Description of the Background Art
Atherectomy catheters having axially reciprocatable, non-rotating blades are described in U.S. Pat. Nos. 5,674,232 and 4,994,067. Other atherectomy catheters are described in U.S. Pat. Nos. 5,571,130; 5,431,673; 5,312,425; 5,242,460; and 5,087,265. A household knife having a V-shaped cutting edge is described in U.S. Pat. No. 2,178,790. Surgical cutters and biopsy devices having axially translatable and/or rotatable cutting blades are described in U.S. Pat. Nos. 5,505,210; 5,395,313; 5,285,795; 5,226,910; 5,250,065; 3,815,004; 4,819,635; 4,696,298; 4,210,146; 3,995,619; 3,705,577; and Re. 33,258.